[lojban] confusion over FUhE-post PEG grammar rule

[".alyn.post." <alyn.post@lodockikumazvati.org>]

I'm confused over the intent of the FUhE-post production in the PEG
grammar:

FUhE-clause <- FUhE-pre FUhE-post
FUhE-pre    <- pre-clause FUhE spaces?
FUhE-post   <- !BU-clause spaces? !ZEI-clause !BU-clause

The ! predicate does not advance the input, so if you walk through
each rule in the FUhE-post production, you try to:

 * not match BU-clause.  If we find one, we no-match immediately
   and stop checking.  The input isn't advanced if we non-match it.
 * the spaces? production will always match the empty string, as
   FUhE-post only appears in FUhE-clause, and FUhE-pre, the rule
   before it, ends with a spaces?
 * not match ZEI-clause.  If we find ZEI-clause, we immediately
   stop checking.  If we don't find one, the input is not advanced.
 * not match BU-clause.  This is where I get confused.  We haven't
   advanced the token stream, and we've already checked for a
   BU-clause earlier.

The final !BU-clause is either:

 * redundant
 * should be something like !(ZEI-clause BU-clause)

Anything I missed?

-Alan
-- 
.i ko djuno fi le do sevzi

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